Freedom, and the Principle of Sufficient Reason: Christian August Crusius’S Criticism of Optimism (1745)

Chapter 4 Banning the Best World, God’s (Supposed) Freedom, and the Principle of Sufficient Reason: Christian August Crusius’s Criticism of Optimism (1745)

Christian August Crusius is an unfamiliar name in conventional accounts of the history of modern philosophy. Yet he was a leading character of the early German Aufklärung, both because of his role as a relevant influence on Kant’s pre-critical thought, and due to the fact that he was one of the most fervent op- ponents of Leibnizian and Wolffian rationalist metaphysics in the eighteenth century. Crusius was born in 1715 near Halle and Leipzig in eastern Germany as the son of a Lutheran pastor. He studied philosophy and theology in the University of Leipzig, became professor of Philosophy at that University in 1750 and five years later professor of Theology. He died in Leipzig in 1775. His main philosophical works are the Dissertatio philosophica de usu et limitibus principii ra- tionis determinantis, vulgo sufficientis (Philosophical Dissertation Concerning the Use and Limits of the Principle of Determinant or Sufficient Reason) (1743), a critical examination of the Principle of Sufficient Reason; the Anweisung, vernünftig zu leben (Guide to Rational Living) (1744), his system of ethics; the Entwurf der nothwendigen Vernunftwahrheiten, wiefern sie den zufälligen ent- gegengesetzt werden (Outline of the Necessary Truths of Reason, as Opposed to Contingent Truths) (1745), his main treatise on metaphysics;1 the Weg zur Gewissheit und Zuverlässigkeit der menschlichen Erkenntniss (Path to the Certainty and Reliability of Human Knowledge) (1747), a system of logic; and the Anleitung, über natürliche Begebenheiten ordentlich und vorsichtig nachzuden- ken (Instruction on How to Reflect Correctly and Cautiously on Natural Events) (1749), his physics.2

1 An English translation of parts of this work can be found in Watkins 2009. 2 Until this day, the best general exposition of Crusius’s life and work is Tonelli 1969. On Crusius’s influence of Kant, see Campo 1953; Ciafardone 1982; Heimsoeth 1926; Heinrich 1963; Kanzian 1993; Marquardt 1885; Tonelli 1966; Treash 1989. On his metaphysics and his criticism of Leibniz-Wolffianism see Carboncini 1986, 1987, 1989, and 1991: 195–217; Krieger 1993; Röd 1984: 261ff.; Roldán 1990; Seitz 1899; Wundt 1945: 230–54.

During his studies in Leipzig Crusius was strongly influenced by the teachings of Adolph Friedrich Hoffmann (1703–1741). Hoffmann had studied under Andreas Rüdiger (1673–1731), who in turn was an important follower of Christian Thomasius (1655–1728), himself a renowned detractor of Wolff’s rationalist philosophy. As is known, Christian Wolff (1679–1754) was instru- mental for the popularization of Leibnizian thought in the eighteenth century (even though the exact relationship between the philosophies of both rationalist thinkers remains controversial and the traditional picture of Wolff as a simple divulgator of Leibniz’s philosophy has been shown to be superficial).3 It is within the Thomasian tradition that Crusius’s philosophy should be thought of. The advocates of this tradition upheld the limited character of human knowledge and with it the impossibility of knowing and explaining entirely the non-empirical nature of reality. They rejected the use of the mathematical method in metaphysics, the Leibnizian theory of pre-established harmony, the doctrine of the universal validity of the Principle of Sufficient Reason, as well as the intellectualistic account of moral agency that Leibniz and Wolff seem to promote. Against this intellectualism, in order to establish a theory of the absolute, undetermined freedom of the will, the Thomasian philosophers propounded the complete independency and priority of the will with respect to the understanding. For this reason, they have been traditionally described as maintaining a radical voluntarism, according to the terminology explained in Chapter 1.4 Accordingly, Crusius opposes Leibniz and Wolff on almost every major issue of their teachings. Yet, it should be noted that the most significant aspect of Crusius’s attack on traditional rationalism is, in fact, his rejection of characteristic motives of Leibniz’s thought, the knowledge of which came most prob- ably directly from the works by Leibniz that could be known in Crusius’s day: the Theodicy, the correspondence with Samuel Clarke, and the Monadology in the German translation of 1720. Those characteristic Leibnizian motives rejected by Crusius are: the general theory of monads, the hypothesis of pre- established harmony, the Principle of Sufficient Reason, and the doctrine of the divine choice the best of all possible worlds. Wolff’s own philosophical and mathematical views seem to have been of secondary interest to Crusius, who locates – much according with the spirit of his times – Wolff’s principal merit in the “reproduction and propagation” of Leibniz’s philosophy (De usu, §10/36). Already in 1743, the year he published the treatise against the Principle of Sufficient Reason, Crusius was convinced that the Leibnizian principles

3 Cf. Hettche 2019; Wilson 1995. 4 Cf. Röd 1984: 258; Tonelli 1969: xvi–xxii; Wundt 1945: 254ff.